Memory expansion device performing near data processing function and accelerator system including the same

ABSTRACT

A memory expansion device includes an expansion control circuit configured to receive a near data processing (NDP) request and a remote memory device configured to store data corresponding to the NDP request according to control by the expansion control circuit. In response to the NDP request, the expansion control circuit performs a request processing operation to perform a read or a write operation on the remote memory device and performs a computation operation using the data corresponding to the NDP request.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119(a) to Korean Patent Applications No. 10-2021-0184439, filed on Dec. 22, 2021, and No. 10-2022-0071298, filed on Jun. 13, 2022, which is incorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

Embodiments relate to a memory expansion device performing a near data processing function and an accelerator system including the memory expansion device.

2. Related Art

As the number of parameters of a deep neural network (DNN) increases, the size of training data increases, and the iterative executions of a learning algorithm increase, it is becoming important to improve the computational performance of an accelerator for operations of the deep neural network.

Operations used by a deep neural network can be divided into arithmetic operations, memory operations, and communication operations, and a matrix multiplication operation performed for a convolution operation and the like typically occupies the largest portion of the operations.

In order to efficiently perform arithmetic operations, a graphic processing unit (GPU) including special arithmetic units that accelerate matrix multiplication, such as tensor cores and matrix cores, may be used.

Improvements of memory operation and communication operation performance lags compared to improvements in computation operation performance, and accordingly, the proportion of time spent in memory operations and communication operations is increasing in the latest deep neural networks.

Recently, near data processing (NDP) and processing in memory (PIM) technology have been introduced, but there is a problem of sacrificing storage space by adding a computation circuit inside the memory device.

SUMMARY

In accordance with an embodiment of the present disclosure, a memory expansion device may include an expansion control circuit configured to receive a near data processing (NDP) request; and a remote memory device configured to store data corresponding to the NDP request according to control by the expansion control circuit, wherein in response to the NDP request, the expansion control circuit performs a request processing operation to perform a memory operation corresponding to the NDP request on the remote memory device, the memory operation including a read operation or a write operation, and a computation operation using the data corresponding to the NDP request.

In accordance with an embodiment of the present disclosure, an accelerator system may include a plurality of host devices each including a processor; a plurality of memory expansion devices; and an interconnect circuit configured to connect the plurality of host devices and the plurality of memory expansion devices, wherein a memory expansion device among the plurality of memory expansion devices includes an expansion control circuit configured to receive a near data processing (NDP) request; and a remote memory device configured to store data corresponding to the NDP request according to control by the expansion control circuit, and wherein in response to the NDP request, the expansion control circuit performs a request processing operation to perform a memory operation corresponding to the NDP request on the remote memory device, the memory operation including a read operation or a write operation, and a computation operation using the data corresponding to the NDP request.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, wherein like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments that include various features, and explain various principles and beneficial aspects of those embodiments.

FIG. 1 illustrates an accelerator system according to an embodiment of the present disclosure.

FIG. 2 illustrates a memory expansion device according to an embodiment of the present disclosure.

FIG. 3 illustrates a control process for a graphic processing device and a memory expansion device according to an embodiment of the present disclosure.

FIG. 4 illustrates a conventional deep neural network operation.

FIG. 5 illustrates a deep neural network operation according to an embodiment of the present disclosure.

FIG. 6 illustrates an expansion control circuit according to an embodiment of the present disclosure.

FIG. 7 illustrates a near data processing (NDP) circuit according to an embodiment of the present disclosure.

FIGS. 8A, 8B, and 8C illustrate tables used in a memory expansion device according to an embodiment of the present disclosure.

FIGS. 9A, 9B, and 9C illustrate software codes of an NDP kernel according to an embodiment of the present disclosure.

FIGS. 10A, 10B, and 10C illustrate tables set by an NDP start packet according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Various embodiments will be described below with reference to the accompanying figures. Embodiments are provided for illustrative purposes and other embodiments that are not explicitly illustrated or described are possible. Further, modifications can be made to the embodiments of the present disclosure that are described below in detail.

FIG. 1 is a block diagram illustrating an accelerator system 1000 according to an embodiment of the present disclosure.

The accelerator system 1000 includes a plurality of host devices 10, a plurality of memory expansion devices 100, and an interconnect network 20 connecting the host devices 10 and the memory expansion devices 100.

In the present embodiment, a request transmitted among the host devices 10, the interconnect network 20, and the memory expansion devices 100 may have a packet structure in which an address and data are formatted in a predetermined form.

The host device 10 includes a processor 11 and a memory device 12. In this embodiment, the processor 11 is a graphic processing unit (GPU) 11, and accordingly, the host device 10 may be referred to as a graphic processing device 10.

The memory device 12 is a memory device exclusively used by the GPU 11, and may be referred to as a graphic memory device 12 or a local memory device 12.

The graphic memory device 12 is not limited to a specific type of memory device, and various memory devices such as a Dynamic Random Access Memory (DRAM), a graphic DRAM, and a High Bandwidth Memory (HBM) may be used.

The memory expansion device 100 includes a near data processing (NDP) function (for example, as shown in FIG. 6 ) and may be referred to as an NDP expansion (NDPX) device 100.

As shown in FIG. 2 , the memory expansion device 100 includes an expansion control circuit 110 and a plurality of memory devices 120. The memory device 120 may be referred to as an expansion memory device 120 or a remote memory device 120.

The expansion control circuit 110 may support a communication function via the interconnect network 20 by performing a switch function.

The interconnect network 20 is a network in which a plurality of graphic processing devices 10 and a plurality of memory expansion devices 100 are fully connected.

In this embodiment, the plurality of GPUs 11 and the plurality of memory expansion devices 100 share an address space.

Accordingly, each GPU 11 may access any of the remote memory devices 120 using a read or write request. Also, in some embodiments, one memory expansion device 100 can access another memory expansion device 100.

FIG. 3 illustrates a control process for the graphic processing device 10 and the memory expansion device 100 according to an embodiment of the present disclosure.

A deep neural network (DNN) application program 1 is compiled by a compiler 2 that supports memory expansion devices.

The compiler 2 generates a GPU kernel 3 performed by the graphic processing device 10 and an NDP kernel 4 performed by the memory expansion device 100.

In the field of computer science, a kernel is a term having various meanings. In the present embodiment, “kernel” is interpreted as having the same meaning as “function.”

A read or write request to the memory expansion device 100 may occur while the graphic processing device 10 executes the GPU kernel 3, and in response to each request, the memory expansion device 100 may execute the NDP kernel 4.

The request generated by the GPU kernel 3 and the NDP kernel 4 corresponding thereto may be predetermined by the compiler 2.

FIG. 4 shows an example of deep neural network (DNN) operations according to a conventional art.

FIG. 4 illustrates a case in which the computation operations are performed in the order of a convolution operation, a batch normalization operation, a rectified linear unit (ReLU) operation, and a convolution operation.

Hereinafter, data input to the deep neural network or output from each layer of the deep neural network is referred to as tensor data.

In the illustrated example of FIG. 4 , the tensor data input for matrix multiplication is provided in advance to the GPU 11.

First, for a convolution operation, the GPU 11 performs matrix multiplication at S1, and stores the multiplication result in the local memory device 12 at S2.

Thereafter, the entire multiplication result is read back from the local memory device 12 at S3, the GPU 11 performs an accumulation operation at S4, and mean and standard deviation are calculated at S5.

Thereafter, the multiplication result is read again in the local memory device 12 at S6, a normalization operation and a ReLU operation are performed at S7, and tensor data, which is the operation result, is stored in the local memory device 12 at S8.

Finally, tensor data is read from the local memory device 12 at S9 for use in a matrix multiplication at S10 for the next convolution operation.

As described above, in the related art, all computation operations are performed in the GPU 11, and read and write operations are frequently performed between the GPU 11 and the local memory device 12 due to insufficient internal buffers in the GPU 11.

In addition, it takes a lot of time to perform the neural network operations because computation operations and memory operations are alternately performed. The memory operation may be represented as a request processing operation.

FIG. 5 shows a deep neural network operation according to an embodiment of the present disclosure.

Like FIG. 4 , FIG. 5 also illustrates a case in which neural network operations are performed in the order of a convolution operation, a batch normalization operation, a ReLU operation, and a convolution operation.

In the present embodiment, the matrix multiplication operation for convolution is performed in the GPU 11, but the normalization operation and the ReLU operation may be performed inside the memory expansion device 100 that is performing a near data processing (NDP) function.

The accumulation operation and calculation operation of mean and standard deviation required for the normalization operation may also be performed inside the memory expansion device 100.

In the illustrated example of FIG. 5 , the input tensor data for matrix multiplication is provided in advance to the GPU 11.

First, the GPU 11 performs a matrix multiplication at S11. The multiplication result is transmitted to the memory expansion device 100 using a write request packet at S12.

In the present embodiment, a write operation for storing data in the remote memory device 120 by a write request at S121 corresponding to the write request packet at S12 and an NDP operation in the NDP circuit inside the memory expansion device 100 at S13 may be simultaneously performed. This may be referred to as an on-the-fly NDP operation.

In the present embodiment, requests for read or write operations of the remote memory device 120 may be divided into requests for which the on-the-fly NDP operation is performed together with the read or write operation and requests for which the on-the-fly NDP operation is not performed with the read or write operation.

Hereinafter, a request for which an on-the-fly NDP operation is performed is referred to as an NDP request, and a request other than the on-the-fly NDP operation is referred to as a normal request.

Accordingly, a write request from the GPU 11 to the memory expansion device 100 may be either an NDP write request or a normal write request, and a read request from the GPU 11 to the memory expansion device 100 may be either an NDP read request or a normal read request. The write request and read request of S12 and S15 of FIG. 5 are an NDP write request and an NDP read request, respectively.

In FIG. 5 , the write operations in S12 and S121 and the accumulation operation S13 may be performed a plurality of times, for example, n times where n is a natural number, respectively. In this case, n depends on the size of the tensor data and the size of the packet.

For example, when tensor data is provided through n write request packets, n write requests at S12 and S121 and n accumulation operations at S13 corresponding to the n write requests may be performed. A write reply may be provided from the remote memory device 120 at S122 per each write request at S121 and a write reply may be provided from the memory expansion device 100 at S123 per each write request at S12.

Thereafter, mean and standard deviation is calculated at S14.

In the present embodiment, the n accumulation operations at S13 and the calculation operation of the mean and standard deviation at S14 may be executed through one NDP kernel. This will be disclosed in detail below.

Thereafter, the GPU 11 reads tensor data from the remote memory device 120 for a second convolution operation at S15.

An on-the-fly NDP operation may be performed while reading tensor data from a remote memory device 120. In the present embodiment, normalization and ReLU calculation operation is performed as an on-the-fly NDP operation at S16.

In FIG. 5 , n read requests are provided to the memory expansion device 100 at S15 and corresponding n read requests are provided to the remote memory device 120. Data may be provided n times from the remote memory device 100 with a read reply at S152 from the remote memory device 120 and n normalization and ReLU calculation operations at S16 may be performed as NDP operations corresponding to the n read requests at S15. Results of the normalization and ReLU calculations at S16 may be provided to the GPU 11 as read replies at S153.

Then, the next matrix multiplication is performed using the normalization and ReLU calculation results at S17.

In the present embodiment, since data is transmitted between the GPU 11 and the memory expansion device 100 through the interconnect network 20, additional time for a communication operation may be required.

However, the on-the-fly NDP operation of the memory expansion device 100 may overlap the memory read/write operation, and thus more time can be saved, and as a result, the overall deep neural network operation time can be significantly reduced.

In FIG. 5 , since the result of the matrix multiplication performed by the GPU 11 is used by the memory expansion device 100, a dependency relationship exists between the GPU operation and the NDP operation.

When a dependency relationship does not exist between the GPU operation and the NDP operation, the GPU operation and the NDP operation may also overlap, and in this case, more time may be saved.

FIG. 6 is a block diagram illustrating an expansion control circuit 110 according to an embodiment of the present disclosure.

The expansion control circuit 110 includes an interface circuit 111, a direct memory access (DMA) circuit 112, and a plurality of NDP request control circuits 200.

The interface circuit 111 transmits packets between the plurality of NDP request control circuits 200 and the interconnect network 20.

Address range of each NDP request control circuit 200 is assigned according to a corresponding remote memory device 120, and the interface circuit 111 determines an address of an input request packet and sends it to a corresponding NDP request control circuit 200.

The DMA circuit 112 may generate a request packet inside the memory expansion device 100 using a conventional DMA technology and may be connected to the interface circuit 111.

For example, the request packet generated by the DMA circuit 112 may have the same form as the request packet provided from the host device 10.

Accordingly, a request generated by one memory expansion device 100 may be internally processed or may be transmitted (for example, through the interconnect network 20) to another memory expansion device.

The plurality of NDP request control circuits 200 are connected between the interface circuit 111 and the plurality of remote memory devices 120 to perform memory operations and NDP operations.

Each NDP request control circuit 200 respectively includes a filter circuit 210, an NDP circuit 300, and a memory controller 220.

The filter circuit 210 identifies whether the request packet provided through the interface circuit 111 is an NDP request packet or a normal request packet. An operation of the filter circuit 210 will be described in detail below.

FIG. 7 is a block diagram illustrating an NDP circuit 300 according to an embodiment of the present disclosure.

The NDP circuit 300 includes a request decoder 310, a request buffer 320, an instruction storage circuit 330, a computation circuit 340, an instruction cache 350, a register address translation circuit 360, a register file 370, and a micro-context storage circuit 380.

The request decoder 310 modifies the request transmitted from the filter circuit 210 so that information necessary for the NDP operation is included and outputs the result of the modification as a decoded request.

The request buffer 320 stores the decoded request.

The instruction storage circuit 330 stores an instruction corresponding to a request.

The instruction is stored in advance in the instruction cache 350, and an instruction corresponding to the request is stored in the instruction storage circuit 330 with reference to the instruction cache 350.

The location of the instruction corresponding to the request may be specified in advance, which will be disclosed in detail below.

The instruction storage circuit 330 includes a plurality of instruction queues 331, and each of the queues of the instruction queues 331 stores a sequence of instructions for a corresponding NDP kernel.

The instructions stored in the instruction queues 331 are provided to the computation circuit 340 to be used for computation operations.

The instruction storage circuit 330 further includes a request queue 332.

The request queue 332 stores a memory request corresponding to an NDP write request or an NDP read request. The memory request may be a write request or a read request.

The memory request stored in the request queue 332 are provided to the memory controller 220 to perform a corresponding read or write operation on the remote memory device 120.

For example, in FIG. 5 , the write request for the write operation at S12 is stored in the request queue 332, and the instructions for the accumulation operation at S13 and the mean and standard deviation calculation operation at S14 are stored in respective queues of the instruction queues 331.

The computation circuit 340 performs a computation operation corresponding to an instruction provided from the instruction queues 331.

In this embodiment, an operation using a scalar data and a vector data, a square root operation, and the like are supported, but the kinds of operations are not limited thereto, and supported operations may be variously designed and changed according to embodiments.

Moreover, a specific circuit design according to an operation may be implemented using a conventionally known circuit technology, and accordingly a detailed description thereof will be omitted.

The instruction cache 350 is a circuit that stores in advance an instruction corresponding to a request.

The register file 370 includes a one or more vector registers and one or more scalar registers used in computation operations.

The register address translation circuit 360 serves to convert a logical address of a register used in the NDP kernel to a physical address of a register included in the register file 370.

The micro-context storage circuit 380 stores a micro-context table. The micro-context will be disclosed in detail below.

The filter circuit 210 shown in FIG. 6 may store the filter table for use in the filtering operation, and the NDP circuit 300 may store the NDP kernel table and the micro-context table to manage information necessary for the execution of the NDP kernel.

In this embodiment, the NDP kernel table is stored in the request decoder 310 and the micro-context table is stored in the micro-context storage circuit 380, but embodiments are not limited thereto.

FIG. 8A shows a filter table, FIG. 8B shows an NDP kernel table, and FIG. 8C shows a micro-context table.

The filter table includes a base address field, an address bound field, a pivot dimension field, a tensor shape field, an NDP kernel ID field, and a filter argument field.

The NDP kernel table includes an NDP kernel ID field, a code location field, a number of static registers field, a number of dynamic registers field, a number of requests per micro-context field, and a number of remaining micro-contexts field.

The micro context table includes an NDP kernel ID field, a pivot index field, a static register base ID field, and a number of remaining packets field.

The meaning of the fields included in each table will be described in detail below.

In order for an NDP kernel to be normally performed when an NDP request packet is transmitted, it is necessary to set information of the tables shown in FIGS. 8A, 8B, and 8C in advance.

In the present embodiment, before transmitting an NDP request packet to the memory expansion device 100, the GPU 11 transmits an NDP start packet to the memory expansion device 100 to initialize the filter table, the NDP kernel table, and the micro-context table.

FIGS. 9A, 9B and 9C are software codes illustrating an example of an NDP kernel executed in the memory expansion device 100.

The illustrated NDP kernel corresponds to an accumulation operation at S13 and the mean and standard deviation calculation operation at S14 of FIG. 5 .

The NDP kernel sequentially performs an initialization operation, a per-request function operation, and a completion operation.

FIG. 9A shows code for the initialization operation.

In the initialization operation, an operation for initializing a necessary register may be performed, and may be performed when an NDP start packet is received.

The code of FIG. 9A shows that the values of the vector registers v0 and v1 are initialized to 0, respectively.

FIG. 9B shows code for a per-request function operation. A per-request function operation is performed whenever an NDP request is received.

For example, in FIG. 5 , the write operation at S12 and the accumulation operation at S13 are performed by transmitting n number of NDP request packets and therefore code of FIG. 9B may be executed n times.

In the code of FIG. 9B, REQDATA and REQADDR represent special purpose registers to store requested data and requested address, respectively.

The code of FIG. 9B shows an operation (VLS) of loading request data REQDATA into the vector register v2, an operation (VADD) of accumulating each element of the vector register v2 into the vector register v0, an operation (VFMA) to raise each element of the vector register v2 to a power of 2 (that is, to multiply each element of the vector register v2 by itself) and accumulate the result thereof into the vector register v1, and an operation (LS, VST) for storing the value of the vector register v2 at the requested address REQADDR.

FIG. 9C shows a completion operation, and the average and standard deviation calculation operation at S14 in FIG. 5 is performed.

In FIG. 9C, FILTERARG represents a special purpose register and is indicated as a filter argument.

First, the filter argument FILTERARG is stored in the register r1. In this case, the filter argument corresponds to an address to store the calculated mean and standard deviation.

The code of FIG. 9C represents multiplying each element of the registers v0 and v1 by 1/4. In this case, 1/4 is used because it is the inverse of 4, which is the number of row vectors that were accumulated in the example.

Thereafter, the mean value stored in the register v0 is stored at the address designated as the filter argument.

Next, the register v0 is updated by raising each element of the register v0 to a power of 2 (that is, by multiplying each element by itself using the VMUL operation), and a variance value obtained by subtracting (VSUB) the value of the register v1 from the value of the register v0 is stored in the register v1.

Thereafter, the value of the register v1 is updated by calculating the square root for each element of the register v1. As a result, the standard deviation is stored in the register v1.

Finally, the standard deviation in the register v1 is stored at the address which is a sum of a value stored in the register r1 as a filter argument and an offset 0x400.

Hereinafter, a technique for performing an NDP kernel of FIGS. 9A, 9B, and 9C in the memory expansion device 100 by transmitting a plurality of NDP write requests from the GPU 11 will be described.

In the present embodiment, the GPU 11 stores the two-dimensional tensor data A in the memory expansion device 100 through an NDP write request.

In the illustrated example, tensor the data is two-dimensional matrix data in which the number of rows X is 4 and the number of columns Y is 32. In the tensor element A_(x,y), x represents a row number and y represents a column number.

The size of the tensor data is 256 bytes, so each tensor element A_(x,y) of the tensor data has a size of 2 bytes.

In the illustrated example, the base address of the tensor data is 0x000 and the address bound is 0x100. That is, when the GPU 11 transmits a write request to an address range of 0x000 to 0x100, the filter circuit 210 may identify the request as an NDP write request.

In the illustrated example, the size of information that can be stored in the write request packet transmitted from the GPU 11 to the memory expansion device 100 is 32 bytes. Accordingly, one request packet can transmit a write request for 16 elements of the tensor data, and a total of 8 write request packets are transmitted to transmit the tensor data.

In this embodiment, when one row is transmitted, the transmission is divided into an upper column group and a lower column group, and a row vector corresponding to the upper column group is referred to as an upper row vector, and a row vector corresponding to the lower column group is referred to as a lower row vector.

Accordingly, in the illustrated example, tensor elements included in one request packet correspond to either A_(x,0) to A_(x,15) or A_(x,16) to A_(x,31).

In this embodiment, a plurality of NDP requests for an upper row vector and a plurality of NDP requests for a lower row vector belong to different micro-contexts.

In the illustrated example, the code for the NDP kernel is stored from the cache memory address 0x300. In this case, the cache memory address indicates the address of the instruction cache 350.

As described above, REQDATA, REQADDR, and FILTERARG indicate special registers used by the NDP kernel, and these may be included in the register file 370.

In this embodiment, REQDATA represents a register that stores 32 bytes of write data, REQADDR represents a register that stores a write-requested address, and FILTERARG represents a register that stores filter arguments.

As described above, before performing the write operation, the GPU 11 transmits an NDP start packet to the memory expansion device 100 to set information in the table shown in FIG. 8 .

The NDP start packet can be identified by the filter circuit 210 and the NDP circuit 300 by using a predetermined format, and information included in the NDP start packet can be decoded to set the information in the tables of FIGS. 8A, 8B, and 8C.

In this embodiment, the NDP start packet includes information related to base address, address bound, pivot dimension, tensor shape, filter argument, code location, number of static registers, and number of dynamic registers, and other information can be derived therefrom. A static register is allocated during an operation for a corresponding micro-context and a dynamic register is temporarily allocated during an operation for a per-request function.

FIGS. 10A, 10B, and 10C show information of a table set by an NDP start packet.

In response to receiving the NDP start packet, a row is added to the filter table of FIG. 10A in which the base address is 0x000, the address bound is 0x100, the pivot dimension is 0, the tensor shape is (4, 32), the NDP kernel ID is 0, and the filter argument is 0x200.

The tensor shape indicates that the tensor data is two-dimensional. The pivot dimension 0 represents that mean and standard deviation calculation is performed column-wisely. If the pivot dimension is 1, row-wise mean and standard deviation calculation is performed. As described above, the filter argument indicates the address where the mean and standard deviation are to be stored.

In the NDP kernel table of FIG. 10B, a row is set in which the NDP kernel ID is 0, the code location is 0x300, the number of static registers per micro-context is 2, the number of dynamic registers is 2, the number of requests per micro-context is 4, and the number of remaining micro-contexts (that is, the number of micro-contexts that are active and have not yet completed) is 2.

The number of requests per micro-context and the number of remaining micro-contexts are calculated and stored.

As described above, in the illustrated example, the request for 16 elements A_(x,0) to A_(x,15) corresponding to the lower row vector and the request for 16 elements A_(x,16) to A_(x,31) corresponding to the upper row vector correspond to respective micro-contexts.

Accordingly, the total number of micro-contexts becomes 2, and since there are a total of four rows in the tensor data, the number of requests per micro-context becomes 4.

In the micro-context table of FIG. 10C, two rows are stored. In one row, the NDP kernel ID is 0, the pivot index is 0, the static register base ID is 0, and the remaining number of packets is 4. In the other row, the NDP kernel ID is 0, the pivot index is 1, the static register base ID is 2, and the remaining number of packets is 4.

The pivot index is information that identifies a micro-context. The number of static registers in the NDP kernel table represents the static registers that can be allocated per micro-context.

In the micro-context table, the static register base ID corresponding to pivot index 0 is set to 0, and the static register base ID corresponding to pivot index 1 is set to 2.

As the NDP start packet is transmitted and necessary information is set in the table, the initialization code of the NDP kernel operates as shown in FIG. 9A.

Thereafter, in the illustrated example, the first write request packet for micro-context 0 is transmitted. In the illustrated example, the address of the first write request is 0x000.

The filter circuit 210 refers to the filter table, recognizes the write-requested address as a packet corresponding to the NDP kernel ID 0, and transmits the request to the NDP circuit 300.

The request decoder 310 decodes a transmitted request with reference to the NDP kernel table and the micro-context table and stores a decoded request in the request buffer 320.

An instruction corresponding to an NDP kernel ID is loaded from the instruction cache 350 with reference to the code location in the NDP kernel table, and the instruction is stored in the instruction queue 331 and the request queue 332.

The instructions stored in the instruction queue 331 are transferred to the computation circuit 340 to perform an accumulation operation, and the write request stored in the request queue 332 is provided to the memory controller 220.

When the first write request packet is processed, the number of remaining packets corresponding to the NDP kernel ID 0 and pivot index 0 in the micro-context table is decreased by 1 and set to 3.

In the same way, the second and third write request packets for micro-context 0 can be processed.

In this example, the write address corresponding to the second write request packet is 0x040 and the write address corresponding to the third write request packet is 0x080.

When the second write request packet is processed, the remaining number of packets corresponding to the NDP kernel ID 0 and pivot index 0 in the micro-context table is decreased by 1 and set to 2.

When the third write request packet is processed, the number of remaining packets corresponding to the NDP kernel ID 0 and pivot index 0 in the micro-context table is decreased by 1 and set to 1.

Finally, the fourth write request packet for micro-context 0 can be processed, assuming that the write address is 0x0C0.

The fourth write request packet can also be processed in the same way, and the number of remaining packets corresponding to the NDP kernel ID 0 and pivot index 0 in the micro-context table is decreased by 1 and set to 0.

In response to the number of remaining packets for micro-context 0 being set to 0, the number of remaining micro-contexts corresponding to NDP kernel ID 0 in the NDP kernel table is decreased by 1 and set to 1.

Thereafter, four write request packets corresponding to the micro-context 1 may be processed in a similar manner.

The per-request function operation of FIG. 9B is performed in response to each write request packet, and finally, the operation result using row vectors of tensor data is stored in two static registers.

The static register number included in the code of FIG. 9B represents a logical register number.

When a program is compiled, a static register number included in the code may be converted into a physical register number of a static register by referring to the logical register number of the static register and a static register base ID of the micro-context table, and this operation may be performed by the register address translation circuit 360.

For example, in the illustrated example wherein the pivot index of the first and second micro-context are 0 and 1, respectively, and the static register base IDs of the first and second micro-context are 0 and 2, respectively (as shown in FIG. 10C), registers v0 and v1 of FIG. 9A represent physical registers v0 and v1 when performing the NDP kernel operation corresponding to the pivot index 0, the registers v0 and v1 of FIG. 9A represent physical registers v2 and v3 when performing the NDP kernel operation corresponding to the pivot index 1.

In the present embodiment, the completion operation of FIG. 9C is performed once per micro-context and in the illustrated example is performed after four request packets are transmitted.

Accordingly, for micro-context 0 the completion operation code of FIG. 9C calculates, for each column in the upper column group, the average and standard deviation corresponding to the lower row vector by using the calculated values for the lower row vector and stores the average and standard deviation corresponding to the lower row vector at a designated address of the remote memory device 120.

In addition, for micro-context 1 the completion operation code of FIG. 9C calculates, for each column in the lower column group, the average and standard deviation corresponding to the upper row vector by using the calculated value of the upper row vector and stores the average and standard deviation corresponding to the upper row vector at a designated address of the remote memory device 120.

Although various embodiments have been described for illustrative purposes, it will be apparent to those skilled in the art that various changes and modifications may be made to the described embodiments without departing from the spirit and scope of the disclosure as defined by the following claims. 

What is claimed is:
 1. A memory expansion device comprising: an expansion control circuit configured to receive a near data processing (NDP) request; and a remote memory device configured to store data corresponding to the NDP request according to control by the expansion control circuit, wherein in response to the NDP request, the expansion control circuit performs: a request processing operation to perform a memory operation corresponding to the NDP request on the remote memory device, the memory operation including a read operation or a write operation, and a computation operation using the data corresponding to the NDP request.
 2. The memory expansion device of claim 1, wherein the expansion control circuit comprises: one or more NDP request control circuits; and an interface circuit configured to receive the NDP request, select an NDP request control circuit from among the one or more NDP request control circuits according to an address of the NDP request, and provide the NDP request to the selected NDP control circuit, and wherein the selected NDP request control circuit is configured to control the request processing operation and the computation operation corresponding to the NDP request.
 3. The memory expansion device of claim 2, wherein the selected NDP request control circuit comprises: a filter circuit configured to identify the NDP request; an NDP circuit configured to produce a request for the request processing operation and to perform the computation operation according to the NDP request identified at the filter circuit; and a memory controller configured to control the expansion memory device according to the request for the request processing operation produced by the NDP circuit.
 4. The memory expansion device of claim 3, wherein the expansion control circuit is further configured to receive a normal request that does not require a computation operation, and wherein the filter circuit is further configured to identify the normal request and to bypass the identified normal request to the memory controller.
 5. The memory expansion device of claim 4, wherein the filter circuit stores a table including address information, and wherein the filter circuit identifies the NDP request and the normal request with reference to the address information.
 6. The memory expansion device of claim 3, wherein the NDP circuit comprise: a computation circuit configured to perform a computation operation corresponding to the NDP request; an instruction storage circuit configured to store an instruction for the computation operation and a request for the request processing operation; and a register file including a plurality of registers for use in the computation operation.
 7. The memory expansion device of claim 6, wherein the NDP circuit further comprise an instruction cache to store a plurality of instructions, and wherein the instruction storage circuit stores an instruction received from the instruction cache corresponding to the NDP request.
 8. The memory expansion device of claim 7, wherein the NDP circuit further comprises a request decoder to perform a decoding operation by using information included in the NDP request, and wherein the request decoder includes an NDP kernel table that associatively stores the NDP request and an instruction cache address corresponding to the NDP request.
 9. The memory expansion device of claim 8, wherein the NDP circuit further comprises: a micro-context storage circuit configured to associatively store the NDP request and a base address for one or more registers allocated for use in the computation operation; and a register address translation circuit configured to generate register address used for the computation operation with reference to the base address.
 10. The memory expansion device of claim 2, wherein the expansion control circuit further includes a direct memory access (DMA) circuit connected to the interface circuit and configured to generate an NDP request, and wherein the interface circuit is configured to provide the NDP request generated by the DMA circuit to the NDP request control circuit or to a device external to the memory expansion device.
 11. An accelerator system comprising: a plurality of host devices each including a processor; a plurality of memory expansion devices; and an interconnect circuit configured to connect the plurality of host devices and the plurality of memory expansion devices, wherein a memory expansion device among the plurality of memory expansion devices includes: an expansion control circuit configured to receive a near data processing (NDP) request; and a remote memory device configured to store data corresponding to the NDP request according to control by the expansion control circuit, and wherein in response to the NDP request, the expansion control circuit performs: a request processing operation to perform a memory operation corresponding to the NDP request on the remote memory device, the memory operation including a read operation or a write operation, and a computation operation using the data corresponding to the NDP request.
 12. The accelerator system of claim 11, wherein the expansion control circuit comprises: one or more NDP request control circuits, and an interface circuit configured to receive the NDP request, select an NDP request control circuit from among the one or more NDP request control circuits according to an address of the NDP request, and provide the NDP request to the selected NDP control circuit, and wherein the selected NDP request control circuit is configured to control the request processing operation and the computation operation corresponding to the NDP request.
 13. The accelerator system of claim 12, wherein the selected NDP request control circuit comprises: a filter circuit configured to identify the NDP request; an NDP circuit configured to produce a request for the request processing operation and to perform the computation operation according to the NDP request identified at the filter circuit; and a memory controller configured to control the expansion memory device according to the request for the request processing operation produced by the NDP circuit.
 14. The accelerator system of claim 13, wherein the expansion control circuit is further configured to receive a normal request that does not require a computation operation, and wherein the filter circuit is further configured to identify the normal request and to bypass the identified normal request to the memory controller.
 15. The accelerator system of claim 14, wherein the filter circuit stores a table including address information, and wherein the filter circuit identifies the NDP request and the normal request with reference to the address information.
 16. The accelerator system of claim 13, wherein the NDP circuit comprise: a computation circuit configured to perform a computation operation corresponding to the NDP request; an instruction storage circuit configured to store an instruction for the computation operation and a request for the request processing operation; and a register file including a plurality of registers for use in the computation operation.
 17. The accelerator system of claim 16, wherein the NDP circuit further comprise an instruction cache to store a plurality of instructions, and wherein the instruction storage circuit stores an instruction received from the instruction cache corresponding to the NDP request.
 18. The accelerator system of claim 17, wherein the NDP circuit further comprises a request decoder to perform a decoding operation by using information included in the NDP request, and wherein the request decoder includes an NDP kernel table that associatively stores the NDP request and an instruction cache address corresponding to the NDP request.
 19. The accelerator system of claim 18, wherein the NDP circuit further comprises: a micro-context storage circuit configured to associatively store the NDP request and a base address for one or more registers allocated for use in the computation operation; and a register address translation circuit configured to generate register address used for the computation operation with reference to the base address.
 20. The accelerator system of claim 12, wherein the expansion control circuit further includes a direct memory access (DMA) circuit connected to the interface circuit and configured to generate an NDP request, and wherein the interface circuit is configured to provide the NDP request generated by the DMA circuit to the NDP request control circuit or to a device external to the memory expansion device. 